An integrative approach to neurocardiologic mechanisms of heart disease risk in professional drivers : application of neuro-psycophysiologic and work environment models

Abstract

Aim: This dissertation aims to apply, develop and integrate neurophysiologic, psychophysiologic, and work environment models, along with behavioral and biomedical risk factors" to provide insight into the neurocardiologic mechanisms of heart disease risk in professional drivers (PD).

Methods: Subjects were male PD, age 25-52: 13 with ischemic heart disease(IHD), 12 hypertensives (HTN), 10 borderline hypertensives (BHTN) and 34 normotensives (NTN), and 23 non-PD controls. Electroencephalographic (EEG) parameters in response to 5 minutes rest and 3 minutes exposure to darkness were: alpha abundance, amplitude and frequency. Alpha abundance in response to headlight glare was assessed and the consequent emotion, finger pulse volume (FPV) and blood pressure responses were examined. Event related potentials (ERP) were assessed by an odd ball paradigm, in which red and green signals reminiscent of traffic light were target and non-target respectively. Occupational stress was assessed using the Job Strain (JS) and Occupational Stress Index (OSI). Type A behavior (TAB) was assessed by means of observation and questionnaire. Other behavioral, occupational and biomedical risk factors were assessed by means of questionnaire.

Main results: After glare exposure the IHD drivers showed significantly more marked blockade of alpha activity, rise in diastolic blood pressure (DBP), persistent fall in FPV and lower expressed mean negative emotion than the other groups. The BHTN group reacted initially to glare with DBP rise and FPV fall. Normotensive PD> age 40 maintained a constant DBP. Anxiety trait and long work hours were associated with heightened central arousal to glare in PD. The IHD drivers showed the smallest amplitude of the N2 component of ERP. The HTN drivers showed the largest N2 followed by the BHTN drivers. Diastolic BP reactivity to the ERP was highest among IHD drivers. Those drivers who recovered baseline levels of alpha activity to the glare exposure, showed a significantly larger N2, compared to those who did not. In response to laboratory darkness exposure alpha abundance diminished significantly for darkness compared to rest period for all groups. IHD drivers were the only group to show significant increase in dominant alpha frequency at darkness. They also had the highest TAB questionnaire scores and the heaviest exposure to professional driving. Type A scores were significantly correlated with dominant alpha frequency during darkness. Low availability of attachment(AVAT) (a means of social support in the general life situation) and special driving hazards best predicted TAB scores in PD. There were significant between group differences with respect to Symbolic Aversiveness at the work place, comparing each driver group with the non-professional driver control group PD were distinguished from the control group by a twice higher total OSI score. A greater body mass index, deadline pressure, amplitude of the N2 and lower fear during driving were independent indicators of HTN-BHTN as opposed to NTN status in PD. Indicators of IHD status as opposed to HTN were longer work hours and more expressed fear during driving. The total OSI and number of smoking years predicted current smoking intensity among PD. BMI was best predicted by professional hours at the wheel, the inverse of JS and of AVAT. Long, irregular work hours were identified as a major stressor by the PD. "Need to always be watchful" was identified as the most difficult aspect of work by the PD with many years in the profession.

Conclusion: Drivers with IHD showed more evidence of immediate denial but from some points of view also more "sensitization" in response to the laboratory stressors manifested by more prolonged reactions than other groups. HTN and BHTN drivers showed different patterns suggesting reversible neuro-psychophysiological strain in response to the laboratory stressors. Amount of exposure to professional driving and Type A behavior were components statistically significantly "explaining" the typical IHD reactions. The directions of causality are unknown in this type of cross-sectional study. The findings, however, point to a possibility that long lasting exposure to long hours of daily professional driving may accelerate the development of a typical IHD reaction pattern that could be part of the cardiovascular etiology. This warrants further studies, preferably longitudinal ones that could elucidate the development of each reaction pattern.